Method for preparing quaternary ammonium salts

ABSTRACT

The specification discloses a method for preparing quaternary ammonium salts by reacting a tertiary amine salt with a 2-oxazoline or 2-oxazine compound.

BACKGROUND OF THE INVENTION

The present invention relates to the preparation of quaternary ammoniumsalts. These are generally prepared by the alkylation of tertiary amineswith alkyl halides, sulfonates or sulfates according to the followingreaction. ##STR1## where X=Cl, Br, I, R"SO₄ ⁻, R"SO₃

These reactions are limited by the availability of the alkylating agentsand in the counter ion which is generated. For example, alkyl phosphatesare not readily available, making it difficult to produce a quaternaryammonium phosphate.

Another method for producing quaternary ammonium sulfates involves thereaction of tertiary amines with ethylenimine in the presence of acid.This reaction results in the following type of quaternary ammoniumcompound: ##STR2## The counter ion "X⁻ " can be varied as a function ofthe acid used. These types of quaternary ammonium compounds are usefulas antistatic agents and in the dying of acrylic fabrics.

SUMMARY OF THE INVENTION

The present invention is a method for preparing quaternary ammoniumcompounds by reacting a tertiary amine salt with a 2-oxazoline or2-oxazine compound of the following formula: ##STR3## where b is zerofor oxazoline and one for oxazine; and

R'₁ -R'₆ are the same or different H, alkyl or aryl substituents whichwill not react with, compete with or sterically interfere with thetertiary amine salt in its ring opening reaction with the oxazoline oroxazine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The primary reaction of the present invention yields a first type ofquat and is basically summarized as follows: ##STR4## where R'.sub.(1-6)=H, alkyl, aryl, with R'.sub.(2-6) being most preferably H;

R₁, R₂, R₃ =alkyl, aryl;

b=zero for oxazoline and one for oxazine;

X=Cl, Br, I, HSO₄, H₂ PO₄, etc.

Acid hydrolysis of the amide function of the first type of quat thenyields a second type quat and acid by product as follows: ##STR5##

The 2-oxazoline and 2-oxazine compounds used in the present inventionare generally known compounds. Methods for their synthesis are discussedin Frump, Chemical Reviews, LXXI, No. 5 (1971), pp. 483-505 at p. 486,in Seeliger et al., Angew. Chemische (International edition) V, No. 10,pp. 875-888 (1966), and in U.S. Pat. No. 4,203,900, which references arehereby incorporated by reference.

2-oxozoline compounds are more readily obtainable than 2-oxazinecompounds. Hence in most commercial applications, "b" in the formulaabove will be zero. Examples of 2-oxazolines which can be used in theinvention include 2-ethyloxazoline, 2-isopropenyloxazoline,2-methyloxazoline, 2,5-dimethyloxazoline, 2-undecyloxazoline and2-phenyloxazoline.

The R'.sub.(1-6) on the 2-oxazoline or 2-oxazine used in this processcomprises a hydrogen atom, an alkyl or aryl group. R'.sub.(1-6) can bethe same or different. R'.sub.(2-6) are preferably hydrogen where R'₁ ispreferably an alkyl or aryl group. Of course where "b"=zero, there willbe no R'₄. Examples of R'.sub.(1-6) substituents include hydrogen,methyl, ethyl, undecyl, stearyl, phenyl, benzyl, hydroxyethyl, andp-nitrophenyl groups.

The only limitation on R'.sub.(1-6) is that it must not compete to anysignificant degree with the tertiary amine salt for opening theoxazoline ring, must not significantly react with the amine and must notsterically hinder the ring opening reaction. The foregoing limitationsare to be considered in the context of a specific reaction system andspecific ingredients which can be added to the system to effectivelyminimize the occurrence of the foregoing undesirable effects.

The R₁, R₂ and R₃ components of the tertiary amine salts used in thepresent invention can be the same or different alkyl or aryl groups.Basically, the only limitation on the particular alkyl or aryl groups isthat, as above for R'.sub.(1-6), they must not interfere with or hinderthe oxazoline ring opening reaction. The alkyl and aryl groups mentionedabove in connection with R'.sub.(1-6) are also operable examples for R₁,R₂ and R₃.

The "X⁻ " counter ion of the tertiary amine salt can be any counter ionavailable in an acid. The examples for "X⁻ " given above are by no meanslimiting. One skilled in the art can tailor the reaction by choosing anyof the broad number of counter ions available. The only limitation onthe counter ion is that it must not significantly compete with thetertiary amine for opening the oxazoline ring.

The tertiary amine is reacted with an appropriate acid to create thedesired tertiary amine salt. Examples of tertiary amines which can beused to create the tertiary amine salts for this reaction includetributylamine, triethylamine, triethanolamine, pyridine anddimethylaniline.

The use of free amines can help control selectivity of the reaction,i.e., insure that the primary reaction is between the tertiary aminesalt and the oxazoline ring. For example, where the R'₁ substituent isvinyl or isopropenyl, the amine or another oxazoline will tend to add atthe double bond. The presence of free amine reduces the amount of doublebond addition. As an alternative to adding free amine, some inorganicbase such as sodium hydroxide can be used to generate free amine duringthe reaction.

Vinyl polymerization inhibitors may be employed where the R' substituentincludes a vinyl group. Examples of vinyl polymerization inhibitorsinclude phenothiazine or MEHQ.

The reaction is generally carried out in a polar solvent such asisopropanol, ethanol, methanol or acetonitrile. The reaction must becarried out under anhydrous conditions to avoid hydrolyzing theoxazoline ring. The stoichiometry for the reaction is basically 1:1, butan excess of the amine salt can be used.

The reaction is preferably carried out at between 100°-125° C. Higher orlower temperatures may be appropriate for specific reactions.

EXAMPLE 1

The production of N-(2-propionamidoethyl)-N,N,N-trimethyl ammoniumchloride is illustrated in Example 1. Ethyloxazoline (3.04 g., 0.03mol), trimethylamine hydrochloride (2.74 g., 0.03 mol) and 20 mlisopropanol were charged into a 45 ml Parr reactor, a stainless steelpressure reactor. The mixture was heated 3 hours at 100° C. The mixturewas then cooled and the solvent and unreacted oxazolines stripped atreduced pressure. Crude product, 5.8 g., crystallized on standing. Theproduct was recrystallized from acetone to yield white hygroscopicneedles. Structure was assigned based on spectral data.

The foregoing reaction can be written basically as follows: ##STR6##

EXAMPLE 2

The production of N-(2-methacrylamidoethyl)-N,N,N-trimethyl ammoniumchloride is illustrated in Example 2. Isopropenyloxazoline (2.5 g., 0.02mol), trimethylamine hydrochloride (2.7 g., 0.03 mol), trimethylamine(0.7 g., 0.01 mol) (added to speed up rection and help controlselectivity) and 15 ml isopropanol were charged into a 45 ml Parrreactor. The mixture was heated for 16 hours at 105° C. The mixture wascooled, diluted with water and stripped at reduced pressure. 6.4 gramsof crude product recovered is a mixture of desired product, unreactedtrimethylamine hydrochloride and some double bond addition product.

The foregoing reaction is written as follows: ##STR7##

The product of Example 2 is a cationic monomer used in the preparationof polymers for water treatment, paper making, cosmetics, mineralprocessing and enhanced oil recovery.

The embodiments of the present invention in which an exclusive propertyor privilege is claimed are defined as follows:
 1. A method forpreparing quaternary ammonium compounds comprising:reacting a tertiaryamine salt with a 2-oxazoline or 2-oxazine compound of the followingformula: ##STR8## where b is zero for oxazoline and one for oxazine;andR'₁ -R'₆ are the same or different H, alkyl or aryl substituentswhich will not react with, compete with or sterically interfere with thetertiary amine salt in its ring opening reaction with the oxazoline oroxazine.
 2. The method of claim 1 which includes the further step ofhydrolyzing the quaternary ammonium compound first obtained to obtain analternative quaternary ammonium compound.
 3. The method of claim 2 inwhich R'₂ -R'₆ are hydrogen atoms.
 4. The method of claim 1 in which R'₂-R'₆ are hydrogen atoms.
 5. The method of claim 4 in which said reactionis carried out in the presence of free amine.
 6. The method of claim 1in which said reaction is carried out in the presence of free amine. 7.The method of claim 6 which includes the further step of hydrolyzing thequaternary ammonium compound first obtained to obtain an alternativequaternary ammonium compound.
 8. The method of claim 7 in which R'₂ -R'₆are hydrogen atoms.
 9. The method of claim 1 in which said oxazoline oroxazine comprises ethyloxazoline.
 10. The method of claim 9 in whichsaid tertiary amine salt comprises trimethylamine hydrochloride.
 11. Themethod of claim 1 in which said oxazoline or oxazine comprisesisopropenyloxazoline.
 12. The method of claim 11 in which said tertiaryamine salt comprises trimethylamine hydrochloride.
 13. The method ofclaim 12 in which said reaction is carried out in the presence of freeamine.
 14. The method of claim 11 in which said reaction is carried outin the presence of free amine.
 15. The method of claim 11 in which avinyl polymerization inhibitor is added to the reaction system.
 16. Themethod of claim 1 in which one of said R'₁ -R'₆ substituents includes avinyl group and a vinyl polymerization inhibitor is added to thereaction system.